The invention relates to a device for displacing a member in a graduated manner inside a tube that is held stationary and that is external to the device, the member being displaced from one end of the tube, relative to which end the device is positioned prior to the displacement. The invention relates in particular to a device for displacing a state verification member, e.g., a crack detection member, in a graduated manner inside a tube that is held stationary. Such a device is, in particular, organized to verify the state of multiple tubes included in a steam generator of a nuclear power plant.
Known devices which make it possible to displace a member in a graduated manner inside a tube that is held stationary, the member being displaced from one end of the tube, are commonly expensive, in particular when the displacement must be performed over a relatively long length. That applies particularly when the member is fixed to one end of a tubular support element which is displaced in translation relative to a support body that is held stationary and that carries it. The length of the tubular element tends to limit the accuracy of the indications obtained from displacement measurements which are performed to determine the position of the member inside the tube in which it is being displaced. Slippage often occurs between the tubular element and the encoder that delivers the displacement indications. That is problematic in particular when the displaced member is a state inspection probe whose location must be determined with accuracy in order to be able to map the inside of the tube as exactly as possible, e.g., during an operation for detecting flaws.
The invention thus provides a device for displacing a member in a graduated and motor-driven manner inside a tube that is held stationary and that is external to the device, the member being displaced from one end of the tube, relative to which end the device is positioned prior to the displacement, the displacement being evaluated by means of at least one position encoder delivering information on the position of the member placed at one end of a tubular element which is mounted to move in translation on a support body for supporting the device.
According to a characteristic of the invention, the tubular element is in the form of a member-carrying worm which is provided externally with longitudinal toothed racks distributed around its periphery, and which is displaced in translation relative to the body which carries it under the action of a first toothed belt which is mounted on the support body, which is driven by a motor fixed to the body, and which is meshed with one of the racks, another of the racks meshing with a second toothed belt which is mounted on the support body and which entrains a position encoder fixed to the body for the purpose of delivering information relating to the position of the member as it is displaced.
According to a characteristic of the invention, the tubular element forming the worm is a flexible tubular element.
According to a characteristic of the invention, the tubular element forming the worm is a hollow tubular element inside which a hollow rotary shaft is received, which shaft is coupled at each of its ends to a respective rotary coupling piece provided with mechanical or electro-mechanical means making it possible to rotate the member by means of a motor fixed to the other end of the worm from said member, and with electrical connection means making it possible to connect the member electrically to a complementary other member via a link electrically interconnecting the two coupling pieces via the rotary shaft.